Function vm_pageout_collect_batch

freebsd/vm/vm_pageout.c:270–311

* Add a small number of queued pages to a batch queue for later processing * without the corresponding queue lock held. The caller must have enqueued a * marker page at the desired start point for the scan. Pages will be * physically dequeued if the caller so requests. Otherwise, the returned * batch may contain marker pages, and it is up to the caller to handle them. * * When processing

 * collected.
 */
static __always_inline void
vm_pageout_collect_batch(struct scan_state *ss, const bool dequeue)
{
	struct vm_pagequeue *pq;
	vm_page_t m, marker, n;

	marker = ss->marker;
	pq = ss->pq;

	KASSERT((marker->a.flags & PGA_ENQUEUED) != 0,
	    ("marker %p not enqueued", ss->marker));

	vm_pagequeue_lock(pq);
	for (m = TAILQ_NEXT(marker, plinks.q); m != NULL &&
	    ss->scanned < ss->maxscan && ss->bq.bq_cnt < VM_BATCHQUEUE_SIZE;
	    m = n, ss->scanned++) {
		n = TAILQ_NEXT(m, plinks.q);
		if ((m->flags & PG_MARKER) == 0) {
			KASSERT((m->a.flags & PGA_ENQUEUED) != 0,
			    ("page %p not enqueued", m));
			KASSERT((m->flags & PG_FICTITIOUS) == 0,
			    ("Fictitious page %p cannot be in page queue", m));
			KASSERT((m->oflags & VPO_UNMANAGED) == 0,
			    ("Unmanaged page %p cannot be in page queue", m));
		} else if (dequeue)
			continue;

		(void)vm_batchqueue_insert(&ss->bq, m);
		if (dequeue) {
			TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
			vm_page_aflag_clear(m, PGA_ENQUEUED);
		}
	}
	TAILQ_REMOVE(&pq->pq_pl, marker, plinks.q);
	if (__predict_true(m != NULL))
		TAILQ_INSERT_BEFORE(m, marker, plinks.q);
	else
		TAILQ_INSERT_TAIL(&pq->pq_pl, marker, plinks.q);
	if (dequeue)
		vm_pagequeue_cnt_add(pq, -ss->bq.bq_cnt);
	vm_pagequeue_unlock(pq);
}

/*
 * Return the next page to be scanned, or NULL if the scan is complete.